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Abstract:When asked to name one proposition in the social sciences that is both true and non-trivial, Paul Samuelson famously replied: 'Ricardo's theory of comparative advantage'. Truth, however, in Samuelson's reply refers to the fact that Ricardo's theory of comparative advantage is mathematically correct, not that it is empirically valid. In this paper we develop and implement an empirical test of Ricardo's ideas. We use novel agricultural data that describe the productivity in 17 crops of 1.6 million parcels of land in 55 countries around the world. We find that a regression of log observed output on log predicted output has a (precisely estimated) slope of 0.84 and an R-squared of 0.93. In our view, these findings offer considerable support for Ricardo's ideas.

Authors:
Costinot, Arnaud (MIT)
Donaldson, Dave (MIT)

JEL Classifications:
F11: Neoclassical Models of Trade

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FiveThirtyEight covered the ongoing debate over teacher evaluation, citing two companion papers that appeared together in the September 2014 issue of the American Economic Review. In "Measuring the Impacts of Teachers" I and II the authors construct "value-added" estimates for teachers in a large urban school district by observing how students' test scores change from year to year as they pass through each teacher's classroom. They find that their teacher value-added scores are not significantly biased and are potent predictors of students' later-life outcomes.

Wonkblog covered an article published this month in the American Economic Journal: Applied Economics. In Saving Lives at Birth: The Impact of Home Births on Infant Outcomes the authors study a sample of over 300,000 Dutch women and find that home birth increases the risk of newborn mortality, especially for low-income women, likely because of reduced access to medical technologies after delivery.

A Wall Street Journalanalysis of potential merger activity in the health insurance industry cited a study published in the American Economic Review. In "Paying a Premium on Your Premium? Consolidation in the US Health Insurance Industry," the authors found that a 1999 merger between two large U.S. health insurers drove up customer premiums and depressed doctors' earnings in certain parts of the country.